It is no surprise that AT&T would quickly follow suit after Verizon Wireless launched its shared data plan last month and today was the day. The new plan allows users to share data across multiple devices and multiple users.

The "Mobile Share" plan provides for unlimited calling and texting and offers 1 gigabyte of data for $85 per month, five bucks cheaper than Verizon's plan. Hungrier users can get 6 gigabytes for $170 per month from either carrier. The plan should be available in late August.

But price is not the main attraction with shared plans. It is more about convenience for the user and stickiness for the mobile operator. And by giving it away, it also formally acknowledges that voice is just another commodity application.

There is no requirements for new customers to adopt a shared-data plan and current customers can keep their existing plans even if it offers unlimited data, whereas Verizon Wireless will allow unlimited data plans only for customers that buy an unsubsidized phone. Verizon Wireless also requires customers to sign up for a shared data plan.

Both plans encourage data use as the operators continue to build out their next generation networks. And it is unclear, without being forced, if customers will chose convenience over unlimited data. Two years after it stopped offering unlimited data plans to new customers, 40 percent of AT&T subscribers maintain their unlimited plans.

Jan Dawson, chief telecoms analyst at Ovum, said that as more consumers use multiple devices with mobile connectivity, there is increasing demand for shared data plans. However, Dawson said Verizon could have done better with its launch.

"We often talk about first mover advantage in this market, and Verizon had an opportunity to benefit from it when it launched. But it made several key missteps and turned what should have been a good news story into a bad news story, leaving the door open for AT&T and other carriers to provide a more compelling offering. AT&T seems to have learned from Verizon’s mistakes and is giving customers more options and a simpler charging structure," Dawson said.

Dawson added that AT&T’s offering has almost identical pricing but important differences in the detail. For example, AT&T isn’t forcing customers into the new plans. Dawson said this is important because they’re not the best deal for all customers. In addition, AT&T’s overage charges for data are much simpler, at a flat $15 per gigabyte, compared with Verizon’s confusing two-tier overage charges.

"There are some subtle differences in the pricing, too, but they won’t make a significant difference to most customers," Dawson said. “What neither Verizon or AT&T’s plans do, though, is deal with the thorny issue of device subsidies."

Dawson said that Verizon’s launch highlighted the confusion that exists about the role of subsidies in the minds of consumers and that nothing in AT&T’s launch will alleviate that. "We still need a fundamental change in the way carriers talk to consumers about device subsidies in order to educate them on the true cost of devices and service plans, but we’re not getting that with this launch."